Alans story is quite correct. It mainly was a scare, which resulted in a
lot of extra bussines for the trade, however there were some cars that
used inferior cast iron for the heads that were prone to the dreaded
valve seat recession, from my mind one was Ford Germany.
Thousands of cars were "converted" to lead free or LPG (even worse,
hotter) unneccesarily. Another example being old Landrovers. Just leave
well alone (if it ain't broke, don't fix it). The cracking of the head
due to retrofitting of valve seats inserts is not unique to the
Healey's. In the unlikely event that valve seat recession shows it it is
early enough to take steps.
I have an old Landrover SIII that has been running on LPG from new
(1974), without any modification or trouble from the exhaust valves or
seats.
Kees Oudesluijs
NL
John Harper schreef:
> Alan
>
> I have a different point of view on this subject. One which might well
> start a new debate.
>
> Something like 20 years ago there was a great panic amongst UK users
> of older cars when leaded fuel was being withdrawn. Many owners of
> 100s asked me what they should do and my suggestion was; do nothing.
>
> Around that time the Vintage Sports Car Club published a 25 page
> document which was the result of significant testing that they had
> carried out on older engines.
>
> It was titled
>
> Valve Seat Recession
> Use of Unleaded Gasoline in Older Engines
>
> It was very comprehensive but the conclusion was that for low
> compression, medium tuned engines such at the 100 the recession due to
> the lack of lead on the valve seat was likely to be virtually non
> existent.
>
> Based on this many 100s that I know are still running around without
> changing valve seats without problems 20 years later.
>
> Now to this I can add another point. As we know the 100 head is very
> prone to cracking across valve seats. One owner I know added seats to
> a perfectly good head but soon found the a fatal crack had appeared
> beyond the valve insert. The conclusion was that as the seat has to
> fitted by interference fit, the extra pressure had caused the crack.
>
> My final point is that if one does get seat recession then all that is
> happening is that the part of the head that is being ground away would
> have to be cut away later when fitting a seat; so why bother.
>
> Regards
>
>
>> While you are at it, have the head set up to run on unleaded.
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